Segmented platen for electrostatic printing



SEGMENTED PLATEN FOR ELECTROSTATIC PRINTING Filed Sept. 6 1967 .G. H.ROBINSON ET AL Feb.

2 Sheets-Sheet 1 F5050 QSIUEEM GENE H. ROBINSON THEODORE H. MORSEINVENTORS' I frfu/fi dz.

' ATTORNEYS United States Patent 3,497,297 SEGMENTED PLATEN FORELECTROSTATIC PRINTING Gene H. Robinson and Theodore H. Morse,Rochester,

N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporationof New Jersey Filed Sept. 6, 1967, Ser. No. 665,914 Int. Cl. G03g 5/02US. Cl. 355-16 Claims ABSTRACT OF THE DISCLOSURE An electricallyconductive platen, for supporting a receiver sheet of variable size, isdivided into conductive segments electrically insulated from each other.The segments may be selectively connected to a power supply so that anelectrical potential is established between the segments over which thereceiver sheet extends and a photoconductive element positioned abovethe sheet. The segments which are not covered by the receiver sheet areelectrically connected to the photoconductive element so that no shortcircuit will be created therebetween. A receiver sheet which covers morethan one segment is sufliciently conductive to bridge the gap betweenadjacent segrnents so that no trace of the gap shows on the developedimage.

BACKGROUND OF THE INVENTION This invention relates to an apparatus forcarrying out a process wherein an electrostatic charge is altered by theaction of actinic radiation, such as light, during exposure to a patternof actinic radiation and the application of an electrical field betweena photoconductive element and a receiving material, where the exposuremay take place simultaneously or immediately after the application ofthe electrical field. To accomplish this, a receiving sheet is placedbetween a photoconductive element, including a suitable support bearinga conductive layer which in turn has a photoconductive layer thereon,and a conductive platen. At the same time that the photoconductiveelement is exposed to a radiation pattern, an electrical field iscreated between its conductive backing and the platen so that anelectrostatic image is placed on the receiving sheet corresponding tothe pattern.

In most prior-art devices, prints are made on only one size sheet ofpaper or receiver wherein the paper is supplied to the machine in sheetform or on a roll which is cut to a preselected length. Other machinesare adapted to utilize sheets of difierent sizes but are not adaptableto the special problems which occur when receiver sheets of varying sizeare charged and exposed at the same station. In this situation, theplaten with the receiver sheet resting thereon is covered by aphotoconductive element. However, if the receiver sheet is smaller thanthe platen and photoconductive element, direct contact will occurbetween the later two causing a short circuit and damage to thephotoconductive element.

SUMMARY OF THE INVENTION The above-mentioned difliculties can beovercome by utilizing the present invention, which, in the embodimentshown, provides a roll of receiver-sheet material which is fed onto asegmented platen. There it may be cut to any one of several preselectedsizes corresponding to the size of one or more adjacent conductiveplaten segments. The segments are electrically insulated from each otherand are connected to one terminal of a DC voltage source. The otherterminal is connected to a photoconductive element which may be placeddown upon the receiver sheet during charging and exposure to a lightimage. By

segmenting the platen, only those sections which are under the receiversheet are connected to the voltage source during an exposure. Thosesegments, which are not under the receiving sheet or receiving paper,but are in direct contact with the photoconductive layer, areelectrically connected to the same potential as the photoconductivelayer. As a result, no short circuit is created between thephotoconductive layer and the platen during charging. The receiver has aconductive backing which bridges the gap between the platen segments sothat an image is placed on the receiver sheet across the gaps. Thus,these gaps do not show up on the receiver sheet when it is developed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic, fragmentary,side-elevation of a printer in which the novel segmented platen of thisinvention may be utilized;

FIG. 2 is a greatly enlarged cross-section of the photoconductiveelement, receiver and segmented platen showing further details of theplaten; and

FIG. 3 is a top plan view of the segmented platen of FIG. 2, taken alongline 33 of FIG. 2, showing the electrical connection for placing thevarious platen segments in the circuit.

DESCRIPTION OF THE PREFERRED EMBODIMENT In accordance with thisinvention, a novel segmented platen S may be used in anelectrophotographic apparatus, such as the electrostatic printer shownin FIG. 1. A receiving sheet R which is made of paper 10, having aninsulating coating 11 on one side and a conducting material, such aslayer 12 on the opposite side, a best seen in FIG. 2. It will beunderstood that conductive layer 12 does not have to be a discretelayer, but may be a conductive material within paper 10. It may be fedfrom a supply roll 13, see FIG. I, mounted for rotation about ahorizontal axis 14 in housing H and then through a pair of horizontalfeed rollers 15 and 16 and onto a support or platen S. The feed rollersmay be driven in any suitable manner, such as by paper feed motor 17connected to roller 16 by belt 18. This platen may be made up of severaladjacent segments having areas for supporting a receiver, such assegments 19, 20, 21, 22, 23 and 24, as best seen in FIG. 3, mounted in abase 25 made of insulating material and having transverse ribs 26 and 27and longitudinal rib 28 between the segments to insulate themelectrically, as shown.

A photoconductive sheet P, which is shown as a flexible sheet but couldbe made of a rigid material, is supported at opposite ends of platen Sby means of spaced brackets 29 and 30. As seen in FIG. 2,photoconductive element or sheet P includes a photoconductive coating orlayer 31 on a transparent conductive layer 32 carried by a transparentsupport 32'. Conveniently, the ends of photoconductive sheet P may beattached to rods 33 and 34 which are received in brackets 29 and 30,respectively. At least rod 34 is made of conductive material and is inelectrical contact with conductive layer 32. This completes theelectrical circuit through wire 35 to a DC voltage source 36. Theopposite side of voltage source 36 is connected through a switchingcircuit 37 by means of wires 38, 39 and 40 to platen segments 19, 20 and21, respectively as further described below.

Bracket 29, which holds one end of the photoconductive element, ismounted on the upper end of front vertical arm 41 at the front of platenS whereas bracket 30 is attached to the upper end of a rear vertical arm42. These arms are each arranged for vertical movement, as shown, andfront arm 41 carries a knife blade 43 which cooperates with a stationarycutter 44 at the front end or platen S to cut receiver R to aproper-length sheet after it has been fed onto the platen. Vertical arms41 and 42 are connected through a suitable linkage mechanism (not shown)to a motor (not shown) so that photoconductive element P may be loweredonto the receiver R before exposure and raised when the receiver ismoved across platen S. When the photoconductive element P issuperimposed on a severed receiving sheet supported by platen S, thephotoconductive element is ready to be exposed to a light image andcharged. Conveniently, as the receiver R is fed onto platen S, it may becut to correspond to the length of segment 19, which might be somestandard length, such as 11 inches, or the receiver might be cut to thelength of segment 19 and combined, which again could be a convenientlength, such as 13 inches. Finally, the receiver may be cut so as tocover the entire platen, including segments 19, 20* and 21, for somestill-further desirable length, such as 14 inches. Similarly, the widthof the receiver might be varied. For example, roll 13 might be 8% incheswide so as to cover only platen segments 19, 20 and 21 or it could be 11inches wide, for example, so as to cover segments 22, 23 and 24 also. Itwill be understood that the sizes mentioned are arbitrary and that othersizes may be chosen as conditions require. Also, a greater or lessernumber of platen segments may be provided to facilitate the use of agreater or smaller number of receiver sizes. By looking at FIGS. 1 and2, it can be readily seen that, unless the receiving sheet extendsacross all of the platen segments, a short circuit would be createdbetween the photoconductive layer and the uncovered platen segments,thereby making the device inoperative.

However, by utilizing switching circuit 37, this problem can beovercome. Thus, turning to FIG. 3, gang switches 45, 46 and 47 may beprovided, which are connected to a knob (not shown) on the front ofhousing H. Suitable indicia may be provided thereon to indicate thelength of paper desired. Thus, by merely turning the knob, the operatorcan accomplish two things. He can adjust the paper feed mechanismthrough switch 45 so that the proper length of receiver will be fed ontothe platen. Thus, when switch 45 is in the position shown, the paperfeed motor 17 will be connected so as to advance receiverR so that itcovers segment 19 only. Secondly, segment 20, which is not covered bythe receiver, will be connected through wire 48, switch 46 and wires 49,50 and to conductive layer 32 so that no short circuit will be createdtherebetween. Similarly, uncovered segment 21 will be connected throughwire 51, switch 47 and wires 52, 50 and 35 to conductive layer 32.

If switch 45 is advanced to the next position to cause a longer lengthof paper to be fed, switches 46 and 47 will also be advanced to the nextposition. This will place platen segment 20 in the circuit through wire48, switch 46 and wires 53 and 38. On the other hand, segment 21, whichstill remains uncovered, will be connected through wire '51, switch 47and wires 52, 50 and 35 to the conductive layer 32. If switch 45 isadvanced to the third position, so that a still-longer length ofreceiving sheet is fed onto the platen which will cover all of segments19, 20 and 21, the circuit to platen segment 20 will still be completed,but this time it will be completed throughwire 48, switch 46, and wires54 and 38. The circuit to platen segment 21 will now be completedthrough wire 51, switch 47 and wires 55 and 38.

Whenever a receiving sheet is used having a width no greater than platensegment 19, 20 and 21, gang switches 56, 57 and 58 will be placed in theposition shown in FIG. 3. Thus, segment 22 is connected by wire 59,switch 56 and wires 60, 50 and 35 to conductive layer 32 to prevent ashort circuit therebetween and to maintain both at the same electricalpotential. Similiarly, segment 23 is connected to the conductive layer32 by wire 61, switch 57 and wires 62, 50 and 35, and segment 24 isconnected by wire 63, switch 58 and wires 64, 50 and 35. 'However, bymoving the gang switches to the alternative position, segments 22, 23and 24 can be connected into the circuit whenever segments 19, 20, and21, respectively, are connected in the circuit. Therefore, in thisalternative position, segment 22 will be connected through wire 59,switch 56 and wires 65 and 38 to voltage source 36. On the other hand,segment 23 will be connected through wire 61, switch 57 and wires 66 and48 to switch 46 so that it will be placed in the circuit wheneversegment 20 is placed therein. Similarly, segment 24 will be connectedthrough wire 63, switch 58 and wires 67 and 51 to switch 47 so that itwill be placed in the circuit whenever segment 21 is. Of course, it willbe understood that additional segments, either longitudinally orlaterally, could be provided, as needed, with additional switchingcircuits. Likewise, fewer segments and switching circuits could beprovided, if desired.

When receiver R is large enough to extend across more than one segment,as in FIG. 2, conductive backing 12 will electrically bridge the gap, asacross ribs 26 and 27 between segments 19 and 20 and segments 20* and21, respectively. Thus, an electrostatic image or charge pattern placedon insulating layer 11 will be formed on the portion thereof extendingacross ribs 26 and 27. This has been found to be true for gaps as largeas inch.

After leaving the platen, the receiving sheet, which now carries anelectrostatic image, is passed around a roller 68 and between it and apressure roller 69 into a developing tank 70 having guide means 71therein for directing the receiving sheet through a toner liquid. Ofcourse, it will be understood that a dry toner system such as a cascadeor cloud system could be used. However, in the examples shown, after thereceiving sheet passes through developing tank 70, it passes over roller72 and between squeegee rollers 73 and 74 and pressure rollers 75 and76, which squeeze excess toner liquid from the paper, and past IR lamp77 to dry the paper and aflix the image thereto. Finally, the sheet isfed through slot 78 in housing H for use.

From the foregoing, it can be seen that the segmented platen of thisinvention may be used with receiving sheets of varying length having aconductive backing which will bridge the gap between adjacent segmentsselectively connected in an electrical circuit to create an electricfield between the photoconductive layer and only those segments whichare under a receiving sheet. Any other segments will be electricallyconnected directly to the conductive layer so that no short circuit willbe created between the photoconductive layer and these other segments.

The invention has been described in detail with particular reference toa preferred embodiment thereof, but it will be understood thatvariations and modifications can be affected within the spirit and scopeof the invention We claim:

1. A platen for supporting receiving sheets of varying size in anelectrostatic printer, wherein a photoconductive element is positionableover a receiving sheet on the platen'and exposable to a light image sothat an electrostatic image is placed on the sheet, said platencomprismg:

a base; and

a plurality of adjacent, spaced, conductive segments mounted on saidbase, said segments having substantial areas for supporting thereceiving sheet, and being electrically insulated from each other.

2. A platen, as set forth in claim 1, further including:

insulating material between said segments.

3. A platen, as set forth in claim 1, including:

two segments in adjacent end-to-end relationship and having a commoncenterline; and

a third segment adjacent to at least one of said two segments, saidthird segment having a centerline generally parallel to said commoncenterline.

4. In an electrostatic printer including:

a platen for supporting receiving sheets of varying size;

a photoconductive element positionable over a receiving sheet on saidplaten;

a voltage source electrically connected between said platen and saidphotoconductive element; and

means for advancing a receiving sheet onto said platen to selectablelengths;

the improvement comprising;

said platen including a plurality of adjacent, spaced,

conductive segments, each segment having a substantial surface area forsupporting a receiving sheet, and being electrically insulated from eachother; and

switch means connected between said segments and said voltage source forselectively creating an electrical potential between saidphotoconductive element and one or more of said segments.

5. In an electrostatic printer, as set forth in claim 4,

the further improvement wherein:

said switch means is responsive to said advancing means so that saidelectrical potential is created between said photoconductive element andthose segments eoverable by a selected receiving sheet length.

6. In an electrostatic printer, as set forth in claim 4,

the improvement further comprising:

the improvement further including:

a receiving sheet supportable on said segmented platen and having aconductive backing which forms an electrical bridge between adjacentsegments covered by said receiving sheet so that an electrostatic imagecan be formed on said receiving sheet across the spaces between saidsegments.

8. In an electrophotographic apparatus including:

a first conductive layer;

a photoconductive layer having a first and second surface, said firstsurface being in face-to-face contact with said first conductive layer;

a second conductive layer in face-to-face contact with said secondsurface of said photoconductive layer, said photoconductive layer andsaid second conductive layer adapted to receive a receiving sheettherebetween, said receiving sheet having an insulating surfacepositionable in virtual contact with said photoconductive layer;

means for creating a charge patten on said insulating surface toexposure of said photoconductive layer to an actinic radiation image;and

means for applying an electrical potential between said conductivelayers to create an electrical field therebetween;

the improvement comprising:

said second conductive layer having a plurality of spaced, conductivesegments which are electrically insulated from each other; and

means connected to said segments for applying a first potential tosegments not coverable by said receiving sheet and said for applying asecond potential to segments eoverable by said receiving sheet, so thata charge pattern may be placed on receiving sheet, said receiving sheetshaving at least one dimension shorter than the corresponding dimensionof said photoconductive layer and first conductive layer withoutcreating a short circuit between the first and second conductive layers.

9. In an electrophotographic apparatus, as set forth in claim 8, thefurther improvement wherein:

said first potential is the same as the potential on said firstconductive layer. 10. In an electrophotographic apparatus, as set forthin claim 8, the improvement further including:

a receiving sheet interposable between said photoconductive layer andsaid second conductive layer, said receiving sheet having:

a conductive material on one side thereof extendable between thosesegments covered by said receiving sheet to provide electrical contacttherebetween so that said charge pattern, will be formed on saidreceiving sheet between said segments.

References Cited UNITED STATES PATENTS 3,003,404 10/1961 Metcalfe et al355-16 X 3,057,275 10/1962 Walkup et al. 35515 3,288,602 11/1966Snelling et al. 96l 3,393,617 7/1968 Gaynor 355-3 JOHN M. HORAN, PrimaryExaminer A. MATHEWS, Assistant Examiner

